Since the method for synthesizing a carbon cluster (hereinafter also referred to as “fullerene”), in which carbon atoms are arranged to form a spherical shape or a rugby ball shape, was established, fullerene has been energetically studied. As a result, many fullerene derivatives have been synthesized.
With respect to specific examples of such fullerene derivatives, methods for synthesizing a fullerene derivative, in which 5 organic groups bind to a fullerene skeleton (hereinafter also just referred to as “penta(organo)fullerene derivative”), have been reported (e.g., Japanese Laid-Open Patent Publication No. Hei 10-167994; Japanese Laid-Open Patent Publication No. Hei 11-255509; J. Am. Chem. Soc., 118 12850 (1996); Org. Lett., 2, 1919 (2000); and Chem. Lett., 1098 (2000)).
Further, since a metal-containing fullerene derivative, in which a fullerene is a ligand, has electronic properties based on characteristics of the metal, it is expected that the fullerene derivative will be successfully applied to electrochemical devices. Cyclopentadienyl metal complex of fullerene, which is derived from a penta(aryl)fullerene derivative, etc., have been reported (Japanese Laid-Open Patent Publication No. Hei 11-255509).
In terms of easiness of production of a device, increase in area of a device, etc., materials having an intermediate phase (mesophase) between a solid and a liquid attract attention as functional materials, which are excellent in charge transport characteristics and physical property of photoelectron, and which can be used in electrochemical devices, and liquid crystal-blended materials comprising a fullerene derivative, etc. have been proposed (e.g., Japanese Laid-Open Patent Publication No. 2003-146915 and Japanese Laid-Open Patent Publication No, 2004-331848). Specifically, exhibition of liquid crystallinity of a carbon cluster derivative based on a fullerene derivative having a shuttlecock-like molecular shape has been reported (Japanese Laid-Open Patent Publication No 2003-146915) Unlike general discotic-type fullerene derivatives, this shuttlecock-shaped fullerene derivative has a cup stack type lamination as a conical molecule (Nature, Vol. 4, 419, 681-(2002)). Therefore, the shuttlecock-shaped fullerene derivative has a column-shaped molecular arrangement which is stabler than discotic-type fullerene derivatives and its use as a liquid crystal material is expected.
However, since the shuttlecock-shaped fullerene derivative has a column-like structure, there are problems that temperature of transition to an isotropic phase is low and that it is difficult to perform rearrangement. Therefore, it is difficult to use the shuttlecock-shaped fullerene derivative as a liquid crystal material.
Further, though it is known that liquid crystalline fullerene-ferrocene dyads and fullerene liquid crystalline dendrimers have a layer structure, it is necessary to add a bulky group to a fullerene skeleton, and therefore it is difficult to obtain a product of interest in good yield.